1. Field of the Invention
The present invention relates to a toner to be used in an electrophotographic process, an electrostatic recording process, or a toner jet process, and also relates to an image forming method using the toner. Furthermore, the present invention relates to a process cartridge which can be removably attached on an image forming apparatus, such as a copying machine, a printer, a facsimile machine, or a plotter, where a toner image is formed on a transfer member by forming the toner image on an image bearing member and transferring the toner image to the transfer member.
2. Description of the Related Art
The electrophotographic process is a process for obtaining an image by forming an electrostatic latent image on an image bearing member such as a photoreceptor having a photoconductive material, forming a toner image by developing the latent image with toner, followed by transferring the toner image on a transfer member such as a sheet of paper, and fixing the toner image on the transfer material by the application of heat and pressure to obtain an image. In general, the process comprises a step of cleaning in which the toner that has failed to be transferred and remained on the image bearing member is cleaned up after the transcription and is then stored as waste toner in a waste-toner container. Then, the above steps are repeated.
In contrast to such a method, JP 5-53482 A proposes an image forming method regarded as a development-cleaning system or a cleanerless system as a system that generates no waste toner. In this document, however, there is no concrete description about the whole configuration of such a system.
In JP 10-307456 A, there is proposed a direct-injection charging method as an environmentally preferable technology without the generation of an active ion such as ozone, by which a development-cleaning system can be attained with a contact-development or non-contact-development method. For example, there is proposed an image forming apparatus in which a developer containing toner particles and conductive charging-promoting particles having a particle diameter of ½ or less of the toner particle diameter are applied in the image forming method having the development-cleaning step using the direct-injection charging method. Such an image forming apparatus does not generate discharged products, so that it is possible to considerably decrease the amount of the waste toner and reduce the size of the apparatus at a lower cost, and provide an excellent image without causing poor charging or dispersion or lowering of light-transmittance for image exposure. Even though a preferable particle diameter of the charging-promoting particles having a conductive property is described, there is no description about a preferable particle diameter distribution of the charging-promoting particles. Therefore, further improvements are required for obtaining stable performance thereof.
JP 60-69660 A suggests the external addition of conductive fine powder of tin oxide, zinc oxide, or titanium oxide in high-resistance magnetic toner particles. However, it has been expected to develop toner in which an external additive more preferably used in injection charging is externally added.
Furthermore, JP 6-345429 A suggests conductive ultra-fine powder of tin oxide subjected to a reduction treatment. However, such a suggestion aims to disperse conductive ultra-fine powder of tin oxide in a polymer to provide the polymer with conductivity and there is no description about an improvement in a frictional charging property by externally adding and mixing a conductive ultra-fine powder of tin oxide in toner particles and also there is no description about the toner to be used in an image forming method having the step of injection charging.